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Chapter 7 - Periodicity and the Periodic Table - PowerPoint PPT Presentation


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Chapter 7 - Periodicity and the Periodic Table. 1778 Diderot's Alchemical Chart of Affinities. 1789 Antoine Lavoisier produced the first modern list of chemical elements, containing among others, the 23 elements of those known. redefined the term "element".

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slide3

1789Antoine Lavoisier

    • produced the first modern list of chemical elements, containing among others, the 23 elements of those known.
    • redefined the term "element".
      • Previously, the metals except mercury were not considered elements.
slide6

1862Telluric Helix or Screw

    • French geologist , Alexandre-Émile Béguyer de Chancourtois
slide7

Law of Octaves

    • John Newlands(1865)
    • noticed a repeating pattern of physical and chemical properties every eight elements
      • reminded him of musical scale
      • applied to lower atomic weight elements but not the larger atomic weight elements
    • never accepted as a law
slide8

Periodic law

    • Dmitri Mendeleev
      • published(Principles of

Chemistry) in 1869

        • one year before Julius Lothar Meyer(although he started his research about 5 years before Mendeleev)
    • created a list of physical and chemical prop.
      • “I began to look about and write down the elements with their atomic weights and typical properties, analogous elements and like atomic weights on separate cards, and this soon convinced me that the properties of elements are in periodic dependence upon their atomic weights.”--Mendeleev, Principles of Chemistry, 1905, Vol. II
slide9

Mendeleev’s table organized by:

    • atomic mass/weight(columns)
    • properties(rows)
      • contained elements that had yet to be discovered
        • eka-aluminum = gallium(68)
        • eka-silicon = germanium(70)
        • eka-boron = scandium(45)
    • possible mistake with Te(128) and I(127)???
slide15

Moseley discovers atomic #(1915)

    • periodic law is revised
      • the chemical and physical prop. of the elements are a periodic function of an increasing atomic #
    • period – rows on periodic table
    • groups/families – columns on periodic table
      • similar e- configuration
      • valence e- - electrons in highest NRG level
        • maximum of 8 e-
slide16

main group elements

    • s and p block elements
slide19

groups 3 thru 6

    • new numbering 13 - 16
    • no particular names
    • properties vary from metallic to nonmetallic
slide20

metals

    • excellent conductor of electricity
      • 100,000x better than nonmetals
    • shiny/luster*
    • good conductor of heat*
    • ductile*
      • drawn out in to thin wire
    • malleable*
      • hammered in to thin sheets
    • tenacious*
      • resist being pulled apart
    • higher melting and boiling pts*
      • * varies among metals
slide21

nonmetals

    • poor conductors of electricity
      • insulators
    • poor conductors of heat
    • many dull in appearance
    • most are brittle
    • lower melting and boiling pts
slide22

metalloids

    • have properties of both metals and nonmetals
    • located along stair step line separating metals from nonmetals
slide23

Halogens – group 7(17)

    • most reactive nonmetals
      • require 1 e- to fill outer NRG level
      • react with most metals to form salts
        • halogen(Greek) – salt maker
slide24

transition metals

    • d-orbital electrons
      • loosely held by nucleus
        • good elect. conductors
        • very malleable
      • last electrons are in various NRG levels
      • some e-config vary from aufbau principle
        • may lose 1, 2 or 3 e-
        • Fe, Cu, Ag
slide25

noble gases(inert gases) – group 8(18)

    • non-reactive
      • only Xe forms a compound
      • full outer NRG level
        • stable e- configuration
slide26

rare earth elements

    • lanthanide series
      • shiny metals
      • similar to alkaline earth metals
    • actinide series
      • unique nuclear structure
      • all are radioactive
slide27

hydrogen

    • most abundant element in universe
      • 75% of all atoms are H
    • not in any group
    • 1 p+ and 1 e-
      • allows for H to bond with many of the elements
    • three isotopes
        • protium(H-1) 1 p+ , 1 e- , 0 no
        • deuterium(H-2) 1 p+ , 1 e- , 1 no
        • tritium(H-3) 1 p+ , 1 e- , 2 no
slide30

7.12 Periodic Trends

trend – a predictable change in a particular direction

      • typically restricted to main group elements
  • atomic radius
    • half the distance between two bonded adjacent nuclei
slide31

periodic trend

    • in a group, as atomic # increases the atomic radii of the atoms increase
      • valence e- are in higher NRG levels
      • more electron shielding
        • e- shielding – blockage of the nuclear charge from reaching outer most e- by inner NRG level e-
slide32

in a period, as atomic # increases the atomic radii of the atoms generally decreases

    • e- are in same NRG level
    • e- shielding constant
    • greater nuclear charge
slide34

ionization NRG

    • NRG added to an atom to overcome the attractive forces holding the e- around the nucleus
    • NRG required to remove an e- from an atom

X + ion. NRG  X+ + e-

Na + ion. NRG  Na+ + e-

Br + ion. NRG  Br+ + e-

    • creates charged atoms = ions
slide35

in a group, as atomic # increases ionization NRG decreases

    • larger atoms
    • more e- shielding
      • less nuclear attraction for outermost e-
        • less NRG required to remove e-
          • Li > Na > K > Rb > Cs > Fr
  • in a period, as atomic # increases ionization NRG generally increases
    • atoms are smaller
    • e- shielding constant
      • greater nuclear attraction
        • more NRG required to remove e-
          • Na < Mg < Al < Si < P < S < Cl < Ar
slide39

metals tend to lose e-

    • oxidation – a chemical reaction in which a substance gains a more positive charge by losing e-

Na  Na+ + e- = oxidation

Na = 11p+ & 11e-

Na+ = 11p+ & 10e-

= LEO

slide40

electronegativity

    • the attraction an atom has for other atoms e-
    • arbitrary scale
      • F is most electronegative = 4
        • other elements based on attraction of F
    • periodic trend
      • in a group, as at. # increases, electronegativity decreases
        • less attraction due to larger atoms and e- shielding
      • in a period, as at. # increases, electronegativity increases
        • greater nuclear attraction
      • most electronegative = upper right corner – F
      • least electronegative = lower left corner – Fr
slide42

e- affinity

    • NRG change associated with the addition of an e- to an atom
      • positive e- affinity(exothermic)
        • X + e- X- + NRG
        • most elements
        • Cl + e-  Cl- + NRG
      • negative e- affinity(endothermic)
        • X + e- + NRG  X-
        • few elements
          • alkaline earth metals, noble gases, zn-subgroup
            • full orbitals
            • Ca + e- + NRG  Ca-
slide43

periodic trend

    • positive e- affinity(only)
      • in a group, as atomic # increases, NRG released decreases
        • less nuclear attraction for the e-
      • in a period, as atomic # increases, NRG released increases
        • greater nuclear attraction for the e-
slide44

nonmetals tend to gain e-

    • reduction – a chemical reaction in which a substance gains e- and becomes more negatively charged

Cl + e- Cl-

Cl = 17p+ & 17e-

Cl- = 17p+ & 18e-

says “GER”

LEO

slide45

ionic size

    • size of ion after the atom has lost or gained e-
    • cations – positive ions
      • created when metals lose e-
      • Na + NRG  Na+ + e-
        • smaller than their atom
        • size varies with # of e- lost
    • anions – negative ions
      • created when nonmetals gain e-
      • Cl + e- Cl- + NRG
        • larger than their atom
        • size varies with # or e- gained
slide50

melting and boiling points

    • melting point - the temperature at which a solid changes to a liquid
    • boiling point – the temperature(at normal pressure) at which a liquid changes to a gas
    • periodic trend(transition metals only)
      • generally, melting and boiling points are directly related to the # of unpaired e- in an orbital
        • more unpaired e- the higher the melting and boiling pts.
    • other elements dependent on various other factors